1. Field of the Invention
The present invention relates to a method of manufacturing a resinous tank in which a through-hole is provided at a side wall portion thereof, and more particularly to a method of manufacturing a resinous tank to which blow molding is applied.
2. Description of the Related Art
As a resinous tank manufactured through blow molding, for example, a washer tank which is applied to a wiper device of a vehicle and contains solutions such as a window washer solution or the like is known.
In this type of washer tank, as shown in FIG. 36, a through-hole 82 for supplying water is formed at the side wall portion of a tank 80. Further, in the vicinity of the through-hole 82, in general, a pump 84 for supplying water is attached to the tank 80 itself. An inlet 86 of the pump 84 is fit the through-hole 82 via a grommet 88. In this way, sealability around the through-hole 82 is guaranteed. When the pump 84 is operated, a washer solution within the tank 80 is absorbed by the pump 84 and discharged from an outlet 90.
As mentioned above, the grommet 88 is interposed between the through-hole 82 of the tank 80 and the inlet 86 of the pump 84 in such a way that the sealability of the through-hole 82 is guaranteed. However, in order to guarantee the sealability, good surface roughness is required at the inner circumferential wall (the surface of the through-hole 82 to which the grommet 88 is adhered) of the through-hole 82. In other words, when the surface roughness of the inner circumferential wall of the through-hole 82 is poor, the adhesion of the through-hole 82 to the grommet 88 deteriorates. As a result, the sealability becomes poor.
Conventionally, the main body portion (the hollow body) of the tank 80 is molded through blow molding, and thereafter, is machined by tools such as a drill or the like. The through-hole 82 is formed and the surface roughness of the seal surface (the inner circumferential wall portion of the through-hole 82) is guaranteed. Therefore, the number of manufacturing processes, the time to manufacture the product, and the cost of manufacturing are increased.
As a result, a manufacturing technique has been proposed in which subsequent machining which uses tools such as a drill or the like is not required, and when the tank 80 is molded through blow molding, the through-hole 82 can be also formed (Japanese Patent Application Publication (JP-B) No. 3-76808).
In accordance with the manufacturing technique described in JP-B No. 3-76808, a tool with a blade which forms a cavity is provided further outwardly than the molding surface (the cavity) of the molding die, a parison is expanded and a hollow body is formed, and thereafter, the side wall portion of the hollow body is cut out (punched) so as to form the through-hole 82. In accordance with this manufacturing technique, after the tank 80 (the hollow body) is molded through blow molding, there is no need to implement subsequent machining which uses tools such as a drill or the like and the tank 80 can be formed at one manufacturing process.
However, in the manufacturing technique described in JP-B No. 3-76808, since the side wall portion of the hollow body is cut out (punched) by the tool with a blade so as to form the through-hole 82, the inner circumferential wall portion (the seal surface) of the through-hole 82 forms a cut surface. Therefore, the surface roughness of the inner circumferential wall portion (the seal surface) is poor (necessary surface roughness cannot be guaranteed), and as a result, the sealability is likely to be poor. Consequently, the tank 80 which is manufactured in accordance with the manufacturing technique described in JP-B No. 3-76808 cannot be applied to a vehicle washer tank or the like.
With the aforementioned in view, an object of the present invention is to obtain a method of manufacturing a resinous tank in which the surface roughness of the seal surface of a through-hole can be made good and this can be realized at a low cost without requiring complicated machining.
A first aspect of the present invention is a method of manufacturing a resinous tank having a through-hole provided at a side wall portion of the tank, comprising the steps of: providing a tool with a blade at one of molding dies beforehand such that a portion of the tool protrudes further inwardly than the molding surface of the one of the molding dies, the tool being columnar and the blade being provided at a distal end of the tool; forming a hollow body by expanding a resin parison within the molding die such that the resin parison is pressed against inner wall surfaces of the molding dies and brought into close contact with the outer peripheral wall of the tool, protruding the blade of the tool further inwardly than the thickness of a general portion (a portion not provided the tool) of the pressed resin parison such that the outer peripheral wall of the tool forms an inner wall surface of the through-hole; completing formation of the through-hole by advancing the tool further into the hollow body, and cutting out a portion of the resin parison hollow body which portion corresponds to the blade of the tool; and removing the tool from the hollow body, opening the molding dies, and removing the hollow body in which the through-hole has been formed.
In the method of manufacturing a resinous tank relating to the first aspect of the present invention, the tool is provided at the molding die beforehand such that the portion of the tool protrudes further inwardly than the molding surface of the molding die. Since the resin parison is expanded within the molding dies, the parison is pressed against inner wall surfaces of the molding dies and brought into close contact with the outer peripheral wall of the tool.
In this state, the blade of the tool protrudes further inwardly than the thickness of the general portion of the pressed resin parison such that the outer peripheral wall of the tool forms an inner wall surface of the through-hole. The hollow body is thereby formed.
Next, when the tool is advanced further into the hollow body, the resin parison hollow body which portion corresponds to the blade of the tool is cut out and the through-hole is formed. Further, the tool is removed from the hollow body, the molding dies are opened, and the hollow body is removed in which the through-hole has been formed. Consequently, the resinous tank is manufactured.
In accordance with a method of manufacturing a resinous tank relating to the first aspect of the present invention, the resin parison is expanded within the molding dies and brought into close contact with the outer peripheral wall of the tool. In this way, the through-hole is formed. Namely, because the inner wall surface of the through-hole is not a cut surface and is formed in accordance with the outer peripheral wall of the tool (because the outer peripheral wall of the tool is the inner wall surface of the through-hole), the surface roughness of the inner wall portion (the seal surface) can be good (the necessary surface roughness can be maintained). Accordingly, the sealability of the through-hole can be guaranteed and the tank can be suitably used for, for example, a vehicle washer tank or the like.
A second aspect of the present invention is a method of manufacturing a resinous tank having a through-hole provided at a side wall portion of the tank, comprising the steps of: providing a convex portion at one of molding dies beforehand such that the convex portion protrudes further inwardly than the molding surface of one of the molding dies, the convex portion being cylindrical so as to correspond to a through-hole to be formed; disposing a tool with a blade, the tool being columnar and the blade being provided at the distal end of the tool within the cylindrical convex portion; forming a hollow body by expanding a resin parison within the molding dies such that the resin parison is pressed against the inner wall surfaces of the molding dies and brought into close contact with a peripheral wall of the convex portion, and molding the inner wall surface of the through-hole by the peripheral wall of the convex portion; completing formation of the through-hole by advancing the tool further into the hollow body and cutting out a portion of the resin parison hollow body which portion corresponds to the blade of the tool, and removing the tool from the hollow body, opening the molding dies, and removing the hollow body in which the through-hole has been formed.
In the method of manufacturing a resinous tank according to the second aspect of the present invention, the convex portion, which is formed cylindrical so as to correspond to a through-hole of the tank, is provided at the molding die beforehand such that the convex portion protrudes further inwardly than the molding surface of the molding die. Further, the tool is disposed within the cylindrical convex portion.
As the resin parison is expanded within the molding dies, the parison is pressed against the inner wall surfaces of the molding dies and brought into close contact with a peripheral wall of the convex portion. In this way, the hollow body is formed in a state in which the inner wall surface of the through-hole is molded by the peripheral wall of the convex portion.
Next, when the tool disposed within the convex portion is advanced further into the hollow body, a portion of the resin parison hollow body which portion corresponds to the blade of the tool is cut out, and the through-hole is formed. Further, the tool is removed from the hollow body, the molding dies are opened, and the hollow body is removed in which the through-hole has been formed. The resinous tank is thereby manufactured.
In accordance with the method of manufacturing a resinous tank according to the second aspect of the present invention, the resin parison is expanded within the molding dies and brought into close contact with the peripheral wall of the convex portion. In this way, the through-hole is formed. Namely, because the inner wall surface of the through-hole is not a cut surface and is formed in accordance with the peripheral wall of the cylindrical convex portion (because the peripheral wall of the convex portion is the inner wall surface of the through-hole), the surface roughness of the inner wall portion (the seal surface) can be good (the necessary surface roughness can be maintained). Further, providing the convex portion at one of molding dies, the seal surface is not apt to be influenced by the shock of cutting out the portion of the resin parison hollow body. Accordingly, the sealability of the through-hole can be guaranteed and the tank can be suitably used for, for example, a vehicle washer tank or the like.
Further, in the method of manufacturing a resinous tank according to the first and second aspects of the present invention, unlike the conventional example, the through-hole is not formed through subsequent machining using tools such as a drill or the like and can be formed at the same time that the hollow body is molded through blow molding. The resinous tank provided with the through-hole can be formed at one manufacturing process and the cost can be reduced.
In this way, in the method of manufacturing a resinous tank according to the first and second aspects of the present invention, the seal surface of the through-hole can be formed with good surface roughness and this can be realized at a low cost without requiring complicated machining.
A third aspect of the present invention is a method of manufacturing a resinous tank according to the second aspect of the present invention, wherein a heater is provided at the blade of the tool, and when a portion of the resin parison hollow body which portion corresponds to the blade is cut out by the blade, the portion is cut out while being melted by the heater.
In the method of manufacturing a resinous tank according to the third aspect of the present invention, when a portion of the resin parison of the hollow body which corresponds to the blade is cut out by the blade, the portion is cut out while being heated and melted by the heater which is provided at the blade.
As a result, when the tool is advanced further into the hollow body so as to cut out the portion of the resin parison hollow body and to form the through-hole, there is no need to apply large pressing force to the cut-out portion of the resin parison. Accordingly, the hollow body (the general portion of the resin parison) is not shifted and moved unnecessarily due to the movement of the tool with a blade, and the resin parison corresponding to the through-hole can be cut out reliably. As a result, the product accuracy further improves. In addition to this, the through-hole can be easily formed even where the holding force of the hollow body (the general portion of the resin parison) by the molding die is low (in other words, the molding dies can be set regardless of the position at which the through-hole is formed), and the degree of freedom in design and the range of application increases.
A fourth aspect of the present invention is a method of manufacturing a resinous tank according to the first and second aspects of the present invention, further comprising the steps of: when the portion of the resin parison hollow body which portion corresponds to the blade is cut out by the blade, having the blade of the tool retain a cut-out piece; and when the tool is removed from the hollow body, removing the cut-out piece along with the tool.
In the method of manufacturing a resinous relating to the fourth aspect of the present invention, when the portion of the resin parison hollow body which portion corresponds to the blade is cut out by the blade, the cut-out piece is retained by the blade of the tool, and further, when the tool is removed from the hollow body, the cut-out piece is removed from the hollow body along with the tool.
Accordingly, the cut-out piece of the resin parison does not drop and remain inside the hollow body. As a result, after the molding dies are opened and the hollow body is removed, there is no need to take out the remaining cut-out piece later, and the processes and the cost can be reduced.
A fifth aspect of the present invention is a method of manufacturing a resinous tank according to the first, second, or fourth aspect of the present invention, wherein the tool or the convex portion is provided in a vicinity of a position of the die-matching portion of a pair of male and female segmental molding dies so as to mold the through-hole.
In the method of manufacturing a resinous tank according to the fifth aspect of the present invention, the tool or the convex portion is provided in a vicinity of a position of the die-matching portion of the pair of male and female segmental molding dies so as to mold the through-hole.
In the die-matching portion of the molding dies, the resin parison (the portion of the resin parison other than the one used for forming the resinous tank) is nipped and held. Accordingly, when the tool or the tool disposed within the convex portion is advanced further into the hollow body so as to cut out the portion of the resin parison hollow body and form the through-hole, the hollow body (the general portion of the resin parison) is not shifted or moved unnecessarily due to the movement of the tool. The portion of the resin parison corresponding to the through-hole can be cut out reliably. As a result, the product accuracy further improves.
A sixth aspect of the present invention is a method of manufacturing a resinous tank according to any of the first through fifth aspects of the present invention, wherein a cavity of the molding dies is formed such that an undercut portion is molded at the hollow body, and the tool or the convex portion is provided in a vicinity of the region at which the undercut portion is to be formed.
In the method of manufacturing a resinous tank according to the sixth aspect of the present invention, the cavity of the molding dies is formed go as to mold the undercut portion at the hollow body. The tool or the convex portion is provided in the vicinity of the region at which the undercut portion of the hollow body is to be formed.
It is, of course, difficult to remove the undercut portion of the hollow body from the molding dies. In other words, the hollow body is reliably held at the molding dies. Accordingly, when the tool or the tool disposed within the convex portion is advanced further into the hollow body so as to cut out the portion of the resin parison hollow body and form the through-hole, the hollow body (the general portion of the resin parison) is not shifted or moved unnecessarily due to the movement of the tool, and the portion of the resin parison corresponding to the through-hole can be cut out reliably. As a result, the product accuracy further improves.
A seventh aspect of the present invention is a method of manufacturing a resinous tank according to the first and second aspects of the present invention, the length of a portion of the tool which protrudes beforehand further inwardly than the molding surface of one of the molding dies is equal to or more than the thickness of the general portion of the pressed resin parison so that the thickness of the resin parison on the blade is reduced. Accordingly, it is easy to cut out the portion of the resin parison hollow body and the seal surface is not apt to be influenced by the shock of cutting out the portion of the resin parison hollow body.
A eighth aspect of the present invention is a method of manufacturing a resinous tank according to the seventh aspects of the present invention, the blade is concave-shaped or convex-shaped so that the thickness of the resin parison on the blade is further reduced. Accordingly, it is easy to cut out the portion of the resin parison hollow body and the seal surface is not apt to be influenced by the shock of cutting out the portion of the resin parison hollow body.